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6. Different axial clearance and preloading methods.

Axial clearance is also a very important factor to consider when selecting lead screw, because the existence of clearance will lead to return error, which directly affects the accuracy of reverse operation. Ball screws are divided into different grades according to the gap. For example, THK is divided into G0(0 and preload), G1(0-0.005), GT(0-0.01), G2(0-0.02) and G3(0-0.05), and the axial clearance increases in turn. NSK is also divided into five grades, namely Z(0 and preload), T(0-0.005), S(0-0.02), N(0-0.05) and L(0-0.3). The values in brackets indicate the range of axial clearance in millimeters. For trapezoidal lead screw, Thomson shows that the axial clearance is between 0.02 mm and 0.25 mm. In order to eliminate the axial clearance between the nut and the screw shaft and improve the transmission accuracy, both ball screw and trapezoidal screw can increase the preload. However, the preloading methods are different. For example, THK and NSK ball screws use nut phase difference for a single nut, while for a double nut, they use pre-compression gaskets or spring plates for pre-compression. On the whole, the axial clearance is smaller for ball screws, and the preloading method is more for ball screws, because the current preloading methods for trapezoidal screws belong to constant pressure preloading method, while ball screws are two types: positioning preloading and constant pressure preloading.

7. Different calculation methods.

When calculating the ball screw, it is necessary to consider the basic conditions such as precision, speed and load required by the system. In which, constant speed torque: T1=(Ta+Tpmax+Tu)/i .. I= the number of teeth on the lead screw side N2/ the number of teeth on the motor side N1, indicating the reduction ratio. Generally, trapezoidal screw only needs a formula, T1=FP/2πη, because trapezoidal screw is suitable for low-speed applications, and there are no problems such as high-speed round trip and high acceleration and deceleration.

8. Structural design of nut decoupling.

When the lead screw is long, the nut is subjected to axial deflection torque or the nut is subjected to axial load, the lead screw shaft inclines or deforms along the radial direction, which may cause uneven stress, jam and vibration, which may lead to increased wear and affect the accuracy.

9. Differences in applications.

Trapezoidal screw is sliding friction, too high speed will produce high heat on the joint surface, which will lead to increased wear. Therefore, trapezoidal lead screw is suitable for applications with light weight and low speed requirement. At the same time, trapezoidal lead screw, because of its low precision, is often more suitable for applications that do not require high precision, such as slow transfer and handling. Ball screw, with low heat and high precision, is usually more suitable for applications requiring smooth motion, high efficiency, high precision and long-time continuous or high-speed motion, such as semiconductor equipment.

10. Example of calculation and selection of ball screw.

Finally, how to choose the ball screw according to the conditions of precision, speed, load and service life? “How to choose ball screw”, contact us and we will share it with you.

The coupling is used to connect the two shafts together. The two shafts cannot be separated when the machine is running. The two shafts can only be separated after the machine is stopped and the connection is disconnected. Do you know what are the classifications of couplings?

Let’s follow the editor to find out:

1. Rigid coupling: It can only transmit motion and torque, without other functions.

2. Coupling: It can transmit motion and torque, overload* protection, in addition, it also has different degrees of compensation performance, such as pin type, friction type, magnetic powder type, centrifugal type, hydraulic type and other couplings .

3. Flexible coupling: A flexible coupling without elastic elements can not only transmit motion and torque, but also have different degrees of axial, radial and angular compensation performance, including gear couplings, universal Toward couplings, chain couplings, slider couplings, etc.

4. Flexible coupling with elastic elements: it can transmit motion and torque; it has different degrees of axial, radial and angular compensation performance; it also has different degrees of damping and buffering effects to improve the work of the transmission system Performance, including flexible couplings with various non-metal elastic elements and flexible couplings with metal elastic elements. The structure of various elastic couplings is different, and the difference is large, and the role in the transmission system is also different.

The speed of the working coupling is high and low. For the two-shaft connection that needs high-speed operation, the structure of the coupling should be considered to have high balance accuracy characteristics to eliminate vibration and noise caused by centrifugal force, and increase the relevant drum-shaped gear coupling The abrasion and heat of the motor reduce the transmission quality and service life. Among them, the diaphragm coupling has better adaptability to high-speed operation.

The shaft system connected by the coupling and its operation. For the connection shaft system with large mass and large moment of inertia, and frequent starting, shifting or reversing, you should consider choosing a spring-elastic pin coupling that can withstand large instantaneous overloads and can buffer and absorb vibration.

When the entire diaphragm coupling enters some sending liquids, first of all, they may cause a series of corrosion to acidic objects, and may cause some dissolution of metals, or they may have various effects on some other ions. A different kind of displacement reaction. Then in this case, some of the original particles can replace each other and deposit on the metal surface, because some oxidants are added to the solution itself, so some different ions in the nitrite are reduced. This can effectively promote a series of oxidation reactions or other chemical reactions on their metal surfaces.

Inspection and repair of clearance between ball screw nut pair and supporting system. When the numerical control machine tool has large reverse error, unstable positioning accuracy and knife marks in the quadrant, the first step is to check whether the screw system has clearance. The detection methods are as follows: put the ball in the center hole of one end of the lead screw with a dial indicator, measure the axial movement of the lead screw, and measure the movement of the worktable with another dial indicator. Turn the screw forward and backward, observe the values reflected on the two dial indicators, and confirm the fault location according to the changes of different values. Specific inspection and repair methods are as follows:

1. Inspection and repair of clearance of lead screw support bearing.

For example, when the dial indicator of the measuring screw rotates forward and backward, the pointer does not swing, indicating that the screw does not move. If the pointer of the dial indicator swings, it means that the lead screw has channeling phenomenon. At this time, we should check whether the back cap of the support bearing is locked, whether the support bearing has worn out and failed, and whether the pre-loaded bearing washer is suitable. If there is nothing wrong with the bearing, just refit it as a preload washer. If the bearing is damaged, it needs to be replaced, re-equipped as a preload washer, and then back the back cap tightly.

2. Inspection and maintenance of clearance produced by double nut pair of ball screw.

Pass the test, if it is confirmed that the fault is not caused by the lead screw movement. It is necessary to consider whether there is a gap between screw and nut pairs, and the detection method in this case is basically the same as the detection of screw movement.

3. Inspection and maintenance of single nut pair.

For single nut ball screw, the gap between screw and nut pair cannot be adjusted. If it is detected that there is a gap between the screw nut pair. First, check whether the thread arcs of the lead screw and nut are worn. If the wear is serious, a complete set of lead screw nuts must be replaced. If the wear is slight, the ball with larger diameter can be replaced for repair.

4. Gap caused by unfixed connection between nut flange and workbench.

This problem is generally easy to be ignored. Because of the long-term reciprocating motion of the machine tool, the screw for fixing the Farah disk is loose, which causes a gap. When checking the gap between the screw and nut, the fault factor should be eliminated first, so as to avoid detours during repair.

5. Maintenance of failures such as unstable movement and excessive noise of ball screw nut pair.

The unstable movement and excessive noise of ball screw nut pair are mostly caused by poor lubrication, but sometimes it may also be caused by improper adjustment of servo motor driving parameters.

Rust treatment and antirust method of linear guide rail. As one of the core components of the equipment, the linear guide rail and the linear shaft play a guiding and supporting role. In order to ensure the high machining accuracy of the machine, it is required that the guide rails and straight lines have high guiding accuracy and good motion stability.

During the operation of the equipment, a large amount of corrosive dust and smoke will be produced during the processing of the machined parts, which will be deposited on the surfaces of guide rails and linear shafts for a long time, which will greatly affect the machining accuracy of the equipment.

And corrosion spots will be formed on the surface of the straight axis of the guide rail, thus shortening the service life of the equipment. In order to make the machine work normally and stably and ensure the processing quality of products, the daily maintenance of guide rails and linear shafts should be done carefully.

Please prepare for cleaning the guide rail-dry cotton cloth and lubricating oil. For example, the guide rail of engraving machine is divided into linear guide rail and roller guide rail. Cleaning of linear guide rail: firstly, move the laser head to the right (or left), find the linear guide rail, wipe it with dry cotton cloth until it is bright and dust-free, add a little lubricating oil (sewing machine oil can be used, but not engine oil), and slowly push the laser head left and right several times, so that the lubricating oil can be evenly distributed.

Cleaning of straight guide rail: move the beam to the inside, open the end covers on both sides of the machine, find the guide rail, wipe the contact areas between the guide rails on both sides and the rollers with dry cotton cloth, and then move the beam to clean the remaining areas. After finishing the use of the linear guide rail, it is necessary to apply anti-rust oil on its surface again.

1. The accuracy grades of linear guide rail are divided into (walking parallelism, taking the guide rail 100mm long as an example), general grade (unmarked /C)5μm, (H)3μm, precision grade (P)2μm, precision grade (SP)1.5μm and precision grade (UP)1μm according to the use of different machines. Preload the slider. Generally, preloading is divided into medium preloading and heavy preloading without preloading. The greater the preloading, the better the rigidity. Load: Generally, at the beginning of selection, it is concluded that 1/3 of rated dynamic load is the upper limit of practical load. Therefore, it is generally ensured that there is no sinking when it is added to medium preloading. If the guide rail is used up and down, it will play a guiding role. How much the slider rises is related to the screw or other transmission methods used, but not to the slide rail and slider.

2. There are basically three kinds of different brands. Usually, the gap effect of light preloading and medium preloading can affect the walking accuracy, load bearing ability and rigidity of the guide rail. And the guide rail with gap is selected, which can reduce the oscillation and impact caused by reciprocating motion to a certain extent.

3. When loading, the slider won’t sink much, so it should be called elastic deformation. If you want to say how much, no guide rail material is marked now, because it can be neglected.